Method and apparatus of codebook transformation for interference mitigation in codebook-based precoding

Abstract

When a transmitter communicating with a first receiver interferes with an adjacent second receiver, the transmitter receives a reference signal from the second receiver in order to transform a codebook to mitigate interference in the second receiver. A channel with the second receiver is estimated through the received reference signal, and a receiving correlation matrix is calculated based on the estimated channel. The inverse of the receiving correlation matrix is calculated from the calculated receiving correlation matrix, and the codebook is transformed using the calculated inverse of the receiving correlation matrix.

What is claimed is: 
     
       1. A method of codebook transformation, in which, when a transmitter communicating with a first receiver interferes with an adjacent second receiver, the transmitter transforms a codebook for mitigating interference in the second receiver, the method comprising
 receiving a reference signal from the second receiver; 
 estimating a channel with the second receiver through the received reference signal; 
 calculating a receiving correlation matrix based on the estimated channel; 
 calculating the inverse of the receiving correlation matrix from the calculated receiving correlation matrix; and 
 transforming the codebook using the calculated inverse of the receiving correlation matrix. 
 
     
     
       2. The method of  claim 1 , wherein a codebook transformation execution command message and an interference mitigation execution command message are received from the first receiver before the receiving of a reference signal. 
     
     
       3. The method of  claim 2 , wherein the reference signal is a signal that can be orthogonal to a reference signal for the first receiver, or separate therefrom. 
     
     
       4. A method of codebook transformation when a transmitter communicating with a first receiver interferes with an adjacent second receiver, the method comprising:
 receiving, by the second receiver, a transmitting correlation matrix measurement request message from the transmitter or the first receiver; 
 receiving, by the second receiver, a reference signal from the transmitter; 
 estimating, by the second receiver, a channel from the transmitter to the second receiver based on the reference signal; 
 calculating, by the second receiver, a transmitting correlation matrix based on the estimated channel; and 
 quantizing, by the second receiver, the transmitting correlation matrix and transmitting the quantized transmitting correlation matrix to the first receiver. 
 
     
     
       5. The method of  claim 4 , wherein the receiving of a reference signal comprises transmitting, by the second receiver, a transmitting correlation matrix measurement response message to the transmitter. 
     
     
       6. The method of  claim 5 , further comprising:
 receiving, by the transmitter, the transmitting correlation matrix measurement response message from the second receiver; 
 determining, by the transmitter, whether the transmitting correlation matrix measurement response message is an acceptance message; and 
 if the transmitting correlation matrix measurement response message is an acceptance message, transmitting, by the transmitter, the reference signal to the second receiver. 
 
     
     
       7. The method of  claim 4 , further comprising,
 after the transmission to the first receiver: 
 receiving, by the transmitter, the quantized transmitting correlation matrix from the first receiver; 
 calculating, by the transmitter, the inverse of the received quantized transmitting correlation matrix; and 
 transforming, by the transmitter, the codebook using the calculated inverse of the transmitting correlation matrix. 
 
     
     
       8. The method of  claim 4 , comprising transmitting, by the second receiver, the quantized transmitting correlation matrix to the transmitter. 
     
     
       9. The method of  claim 8 , comprising:
 receiving, by the transmitter, the quantized transmitting correlation matrix from the second receiver; 
 calculating, by the transmitter, the inverse of the received quantized transmitting correlation matrix; and 
 transforming, by the transmitter, the codebook using the calculated inverse of the transmitting correlation matrix.